Chainsaw Glossary
Every technical term used across this database, defined. Specification terms link to the models that publish them.
Classification
- Fuel Type Specification
- The energy source the saw runs on: a petrol and two-stroke oil mixture, a battery pack, or mains electricity through a cord. It is the choice that shapes almost every other characteristic of the machine.
- Intended Use Specification
- The class of user a saw is built for: consumer, semi-professional or professional. It summarises the duty cycle the machine is designed to sustain rather than any single technical measurement.
- Rear-handle saw
- The conventional chainsaw layout, with the throttle handle behind the engine and a wrap or front handle across the top, designed to be held with both hands. It is the correct configuration for essentially all ground-level work.
- Top-handle saw
- A compact chainsaw whose rear handle sits on top of the machine rather than behind it, allowing controlled one-handed operation. It is designed for arborists working aloft in a tree on rope and harness.
Cutting
- Chain Pitch Specification
- The distance between any three consecutive rivets on the saw chain divided by two, expressed in inches. It is the dimension that must match the drive sprocket and the bar nose, and the common sizes are 1/4", .325", 3/8" (including 3/8" low profile) and .404".
- Chain Speed Specification
- The linear speed at which the chain travels around the guide bar, in metres per second, normally quoted at maximum engine speed. It is determined by engine rpm, the number of teeth on the drive sprocket and the chain pitch.
- Chain gauge
- The thickness of the drive link tang that rides inside the guide bar groove, given in inches. The common gauges are .043", .050", .058" and .063", and the chain gauge must match the bar exactly.
- Drive links
- The toothed links on the underside of the chain that engage the drive sprocket and run in the bar groove. Their count is what determines the chain's overall length for a given bar.
- Maximum Bar Length Specification
- The longest guide bar, in centimetres, that the manufacturer approves for the saw. Fitting anything longer overloads the engine and clutch and usually voids the warranty.
- Raker (depth gauge)
- The small rounded projection immediately ahead of each cutter on the chain, which limits how deep that cutter can bite into the wood. The height difference between the raker and the cutter's top plate sets the chip thickness.
- Recommended Bar Length Specification
- The guide bar length, in centimetres, that the manufacturer considers the best match for the saw's power. It is the length the machine is normally supplied with and the one that gives the best balance of cutting reach and cutting speed.
- Semi-chisel vs full-chisel chain
- The two main cutter profiles on saw chain: full chisel has square-cornered cutters that slice fastest in clean wood, while semi-chisel has rounded corners that stay usable much longer in dirty or frozen conditions. The cutting corner geometry is the only real difference.
- Sprocket-nose bar
- A guide bar with a small toothed roller wheel set in its tip, so the chain rolls around the nose instead of sliding over it. The alternative is a hard-nose bar, in which the chain slides across a solid, usually stellite-faced tip.
Engine
- Decompression valve
- A small button-operated valve that vents part of the cylinder pressure during starting, making the engine much easier to pull over. It closes automatically as soon as the engine fires.
- Easy-start system
- A starter mechanism that uses a spring between the recoil rope and the crankshaft to store the energy of a slow pull and release it in one burst, turning the engine over for you. Manufacturers market it under names such as SmartStart, EasyStart or Soft Start.
- Engine Displacement Specification
- The swept volume of the chainsaw's cylinder, measured in cubic centimetres (cc). It is the single figure most often used to place a petrol saw in its size class, because displacement broadly tracks both power and weight.
- Idle Speed Specification
- The engine speed, in revolutions per minute (rpm), at which the saw runs with the throttle released. It must be set low enough that the clutch stays disengaged and the chain does not move.
- Maximum Speed Specification
- The highest engine speed the saw is designed to reach, in revolutions per minute (rpm), usually quoted with the bar and chain fitted. It is the reference point for carburettor tuning and for the chain speed figure.
- Power Output Specification
- The maximum power the engine or motor delivers, stated in kilowatts (kW). It determines how well the saw holds chain speed when the cutters are loaded in the cut, rather than how fast it spins free.
- Power Output (HP) Specification
- The same maximum power figure expressed in horsepower (hp) instead of kilowatts. One kilowatt equals approximately 1.34 hp.
- Two-stroke mix ratio
- The proportion of petrol to two-stroke oil that a combustion chainsaw runs on, expressed as a ratio such as 50:1 or 40:1. The engine has no separate oil sump, so this mixture is the only lubrication the crankshaft and piston receive.
Maintenance
- Automatic chain oiler
- The pump that continuously feeds bar and chain oil from the oil tank onto the guide bar while the saw is running. Most are driven off the engine so that oil delivery rises with chain speed, and many are adjustable.
- Bar and chain oil
- A dedicated tacky lubricant fed to the guide bar to lubricate the chain, the bar rails and the nose sprocket. It contains adhesion additives so that it clings to a chain moving at high speed rather than being flung straight off.
- Chain tension
- How tightly the chain is drawn against the underside of the guide bar. Correctly tensioned, the drive links stay in the bar groove when the chain is lifted at the middle of the bar, and the chain can still be pulled around by hand.
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Safety
- Anti-vibration system
- The set of rubber buffers or steel springs that separate the engine unit from the handles, reducing the vibration transmitted to the operator's hands. Its effectiveness is what the declared front and rear handle vibration figures measure.
- Chain brake
- A safety device that stops the chain almost instantly by clamping a steel band around the clutch drum. It is triggered either by pushing the front hand guard forward or, on inertia-activated saws, automatically by the sudden rotation of a kickback.
- Chainsaw chaps and PPE
- The personal protective equipment worn for chainsaw work: cut-resistant leg protection (chaps or trousers), a helmet with face screen and ear defenders, gloves and steel-toed boots. Cut-resistant garments contain long loose fibres that pull out, jam the drive sprocket and stall the chain on contact.
- Kickback
- The violent upward and backward rotation of the guide bar towards the operator, caused when the upper quadrant of the bar nose — the kickback zone — contacts wood, or when the chain is pinched in the top of the cut. It is the leading cause of serious chainsaw injuries.
- Sound Power Level Specification
- The total acoustic energy the machine radiates in all directions, in dB(A), independent of where the listener stands. In the EU the guaranteed sound power level is the value that must appear on the machine's noise label.
- Sound Pressure Level Specification
- The A-weighted noise level measured at the operator's ear position, in dB(A). It is the figure that describes what the person holding the saw is actually exposed to.
- Vibration Front Handle Specification
- The vibration transmitted to the operator's hand at the front handle, expressed as an acceleration in m/s². It is one of the two figures used to estimate daily hand-arm vibration exposure.
- Vibration Rear Handle Specification
- The vibration measured at the rear handle, in m/s², where the throttle hand grips the saw. It is declared alongside the front handle figure because exposure is assessed for both hands.
Tank
- Fuel Tank Capacity Specification
- The volume of the fuel tank in litres, holding the petrol and two-stroke oil mixture on a combustion saw. Together with fuel consumption it sets how long the saw runs between refills.
- Oil Tank Capacity Specification
- The volume in litres of the reservoir that feeds bar and chain oil to the guide bar. This oil lubricates the chain as it runs and is consumed continuously while cutting.
Technique
- Bucking
- Cutting a felled trunk or a fallen limb crosswise into shorter lengths. It is the stage of the work that produces firewood or sawlogs once the tree is on the ground.
- Felling
- The operation of cutting down a standing tree so that it falls in a controlled direction. It is done with a directional notch on the intended fall side and a back cut that leaves an uncut hinge of wood to steer the tree.
- Limbing
- Removing the branches from a felled tree to leave a clean trunk. It is normally worked from the base towards the top, cutting the branches on the far side of the trunk so the stem stays between the saw and the operator.
Weight
- Weight (without bar and chain) Specification
- The mass of the powerhead alone in kilograms, excluding the guide bar, the chain and any fuel or oil. It is the standard figure manufacturers publish so that saws can be compared on a common basis.
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